The invention relates to actuators and zone valves for heating and cooling systems.
Zone valves are often utilized in hydronic heating and cooling systems. The zone valves isolate specific areas or xe2x80x9czonesxe2x80x9d of the system. Typically, each zone valve is controlled by a thermostat, which causes the valve to open and close to achieve desired temperature changes.
Conventional zone valves are typically actuated by either a heat motor or an electric motor. In valves with a heat motor as the actuator, an electrically heated element causes linear movement of an actuating element that, in turn, opens the valve. In valves with electric motors, the motor and associated gears move a valve member between closed and open positions (e.g., a rubber plunger moved away from a seat or a ball element moved through a 90 degree rotation).
Conventional motorized zone valve actuators employ a motor which is energized in one direction by a source of power, held in some predetermined position by a mechanical or electrical braking means, and then returned to its original position by a spring.
Giordani, U.S. Pat. Nos. 5,131,623 and 5,540,414, describe zone valves for hydronic heating or cooling systems in which a motor-driven actuator rotates a ball valve through about a 90xc2x0 rotation, between closed and opened positions. The motor rotates the valve from its normal position, which may be either open or closed, to the opposite position, e.g., if the valve is normally closed from the closed to the open position. When the motor is de-energized, the valve is returned to its normal position by a spring so confused that it provides sufficient restoring torque to overcome the frictional torque of the ball valve.
Carson, U.S. Pat. No. 3,974,427, discloses a motor control apparatus having an electric motor which is driven in one direction by an alternating current power source and in the opposite direction by a spring. Holding or braking of the motor is accomplished by applying a source of direct current power to magnetize the motor and hold it in a predetermined position after the alternating current power source is removed. This holding or braking action is removed by taking away the direct current power source and momentarily applying an alternating current power source to the motor, thereby de-magnetizing or degaussing the motor so that it is free to return to its initial condition under the power of the spring.
Fukamachi, U.S. Pat. No. 4,621,789, discloses a valve mechanism in which the valve is prevented by a physical stopper from moving any further after it has moved to an open or closed state.
Botting, et al., U.S. Pat. No. 5,085,401, discloses a valve actuator in which the motor makes an electrical contact after rotating a predetermined distance, causing deenergization of the motor.
Fukamachi, U.S. Pat. No. 4,754,949, discloses a valve actuator in which the rotation of the valve by a predetermined amount causes electrical contacts to be turned off, stopping the rotation of the actuator motor.
Some motorized valve actuator systems employ a fail safe energy system to provide power to the actuator motor in the event that the main power source is lost. Strauss, U.S. Pat. No. 5,278,454, discloses an emergency, fail safe capacitive energy source and circuit which is used to power an air damper actuator or a valve actuator. A sensor detects loss of power to the valve actuator circuit or motor, activating a switch which connects a bank of capacitors to the motor, with the appropriate polarity to drive the actuator back to its fail safe position. No provision is made for interrupting the connection between the capacitors and the motor when the fail safe position is reached, and thus the motor appears to work against a mechanical stop defining the fail safe position.
The invention features an actuator in which a sensor detects when the valve has reached desired position, and controls a switch that shuts off the motor driving the valve. The invention makes it unnecessary to rely on a mechanical stop or a return spring to put the valve in a desired position. For example, a valve can be moved from open to closed and from closed to open, without relying on a mechanical stop or return spring. And switching a valve from normally-open to normally-closed can be done simply by throwing a single switch.
In one aspect, the invention features an actuator for actuating a valve in a hydronic system, wherein the valve has a first position in which fluid flow may occur along one path and a second position in which fluid flow is either blocked or may flow along another path. The actuator includes: a motor coupled to the valve, wherein rotation of the motor changes the position of the valve from one of the first and second positions to the other of the positions; a switch controlling the delivery of electrical power to the motor, the switch having a closed position in which electrical power is delivered to the motor and an open position in which power is not delivered; a sensor configured to detect the arrival, of the valve at the first and second positions; and circuitry connected to the sensor and to the switch, the circuitry being configured to respond to the detection by the sensor of the arrival of the valve at one of the first and second positions by opening the switch to stop delivery of power to the motor.
Preferred implementations of the invention may include one or more of the following features: The sensor may be configured so that the output of the sensor changes state upon the arrival of the valve at a desired position. The sensor may have two states, and a change of state in its output occurs at approximately the moment when the valve, having begun to move from one of the first and second positions, reaches the other of the position. The motor may rotate the valve in a single direction. An electrical power storage element (e.g., a capacitor) can be included in the actuator for providing power for driving the motor, sensor, and circuitry (e.g., when power to the actuator is lost). The circuitry for controlling the actuator can be provided by an integrated circuit chip. The valve may be a ball valve. The sensor may be an optical sensor. The actuator may have projections on a member that rotates with rotation of the valve and the projections may cause the sensor to become blocked and unblocked, and arrival of the valve at a position corresponds to blockage of the sensor by a projection either ceasing or beginning. The actuator may include a clutch for manually rotating the valve, and the position of the clutch may provide an indication of the angular position of the valve. The actuator may include a worm gear drive between the motor and the valve. A default-position selection switch may be included to enable the actuator and valve to be transformed from a normally-open valve to a normally-closed valve by movement of an electrical switch.
In a second aspect, the invention feature a zone valve for use in a hydronic system, in which the valve includes a ball element; a valve casing enclosing a ball element; a valve seat in contact with the ball element and the valve casing, the valve seat having a notch to receive an O-ring; an O-ring installed in the notch; a metallic, springy washer positioned in a compressed state within the valve casing in such a configuration as to provide an approximately constant force on the valve seat; and wherein the notch is shaped so that the axial force causes the O-ring installed in the notch to be compressed to improve a seal between the valve seat and an internal bore of the valve casing.
In a third aspect, the invention features operating a hydronic valve actuator by, prior to initiating movement of the valve, determining the charge on a capacitive power source and determining the energy required to complete the valve movement prescribed, and then deciding to initiate movement only if the charge on the capacitive power source is sufficient to provide the energy required to complete the movement.
In a fourth aspect, the invention features a hydronic valve actuator including a motor for driving the valve, wherein rotation of the motor changes the position of the valve from one of the first and second positions to the other of the positions; a gear assembly coupling the motor to the valve, wherein the gear assembly includes a worm gear; and a knob shaped to be turned manually either by grasping or by use of a tool; a clutch assembly connecting the knob to the valve stem and to the gear assembly, wherein the clutch assembly can be moved between engaged and disengaged modes, wherein in the engaged mode the gear assembly and worm gear are engaged with the valve stem so that the motor can turn the valve, and in the disengaged mode the gear assembly and worm gear are disengaged from the valve stem so that the valve can be turned using the knob.
Preferred implentations of this aspect of the invention may include one or more of the following features: The clutch assembly may be disengaged by pushing the knob axially. The clutch assembly may include teeth on two rotating members that are separated by axial motion of the knob to disengage the clutch. The knob may have a marking indicating the position of the valve.
Other features of the invention will be apparent from the following description of preferred embodiments, including the drawings, and from the claims.